The invention concerns a novel and improved locking fastener, such as a lock nut, and more particularly a lock nut of a type which is adapted to be staked or otherwise fixed in engagement with an aperture through a generally flat workpiece to receive a threaded component, such as the shank of a screw-type fastener for affixing another structure or element to the workpiece. More particularly, the invention relates to a novel lock nut having a configuration for positively holding the lock nut in engagement with the workpiece and against rotation in response to advancement and rotation of a mating fastener with respect to the lock nut for advancing and seating relative thereto, for securing together of the workpiece and other element or structure.
A serious problem in joints secured together by threaded members is the possibility of joint separation due to one or both of the mating threaded members backing off. Generally, this can occur when the joint and fasteners are subjected to vibration.
Similarly, in joints utilizing a lock nut of the type which is physically affixed or secured to a workpiece or to one of the members to be secured together to form the secured joint, rotation of the nut member during driving and seating of a mating screw-type fastener should be avoided. Heretofore, such rotation has generally been opposed by the force of crimping wherein a locking neck or similar extending member or portion of the nut member is physically crimped, usually by a cold forming or deformation type of operation, to the workpiece or other member to which it is to be secured. While such crimping or staking forces may reliably hold the nut in engagement with the workpiece or other member, the crimping is usually done by generally axially applied forces, such that the lock nut may not reliably resist rotational forces.
More specifically, the lock nut may have some neck or other extension which extends through an aperture in a workpiece and which is deformed or crimped over to engage the nut with the workpiece such that it cannot be easily withdrawn. However, the lock nut may remain engaged with the through opening and yet be subject to rotation relative to the workpiece, either through initial inadequate application of crimping force to oppose rotation, or later loosening of the crimping or staking parts or portions. Such loosening may not be sufficient to permit withdrawal or disengagement of the lock nut from the workpiece but yet be sufficient to permit some amount of rotation thereof. When permitted some degree of rotational movement, the nut may later vibrate excessively when subjected to vibrational forces, thereby loosening the secured joint.
Such rotational forces are particularly brought to bear upon engagement and driving of a mating threaded screw-type fastener relative to the lock nut. Particularly in applications where relatively high torque is used to seat the mating fastener, relatively high torque forces may also be transmitted to the lock nut, particularly during the latter part of the driving and final seating of the threaded mating fastener relative to the lock nut.
It has been heretofore proposed to provide various generally radially extending projections, ribs or serrations on the underhead surfaces of screw-type fasteners, as well as on the surfaces of nuts which face the workpiece surface. However, the purpose of these serrations has been to prevent rotation of both screw and nut members after securing of the joint, for example in response to vibration or the like. As such, such serrations or other gripping structures have generally been arranged in a counterclockwise direction in order to resist rotational forces in a counterclockwise direction which would tend to cause relative disengagement of the screw and nut.
In contrast, the present invention recognizes, that in order to avoid rotation during driving of the screw relative to the nut, it is just the opposite, that is, clockwise rotational forces which are experienced and are to be resisted by the lock nut. Moreover, it is not believed that such locking serrations have been proposed heretofore with respect to a lock nut, i.e., of the type which is positively engaged with a workpiece or other member to be joined by the lock nut and mating fastener.
The above discussion relates to a generally standard thread arrangement where the fastener has a right hand thread. Of course, if the fastener system uses the less conventional left hand thread, the orientation of the ribs for a system in accordance with the present invention would be opposite, that is the ribs would be disposed counterclockwise.